Parallax error avoidance for a touch screen system

Claim 2

The process of compensating for parallax-induced errors associated with use of an electronically generated visual display which is viewed through a medium that is prone to causing apparent image displacement from parallax distortion and wherein touching by the user of one or more discrete areas causes actuation of a touch responsive means, comprising the steps of : determining the amount of visually apparent shift caused by parallax from said medium; assigning a guard band around each area of the electronically-generated visual display which is to receive selected touch actuation with said band (1) having a width which incorporates an area correlated to said determined apparent enlarged size of the surrounded area caused by said parallax distortion; and (2) responding to touching within said band area by generating a signal for indicating to the touch responsive means that said surrounded area was touched.

Claim 3

The process in accordance with Claim 1 wherein said determining step further includes the step of selecting the maximum angular displacement from perpendicular to the surface of the display for which said guard band shall provide compensation.

Claim 4

The process in accordance with Claim 2 for use with a display composed of a cathode ray tube (10) having a transparent touch sensitive screen overlay (12), said determining step including the step of determining the parallax shift at the said selected maximum angular displacement through the combined media of said tube and said screen.

Claim 5

The process of avoiding parallax-induced errors in an electronically-generated display visible at a surface through a plate (20) of a thickness T of transparent media having a refraction index R where the display is to function as an input device to a data processing system (18), or the like, by touching of areas associated with the display comprising the steps of : determining the maximum angle A from perpendicular from the said display surface for which touch selection is allowed free from parallax-induced errors; and providing a guard band (36-39) around each touch-selective area (32-35) of the display where the width P of the guard band is the product of T times tan A2 where A2 is the reciprocal of R divided by sin A.

Claim 6

The process of avoiding parallax-induced errors in an electronically-generated display visible at a surface through a plate (20) of a thickness T of transparent media having a refraction index R where the display is to function as an input device to a data processing system (18), or the like, by touching of areas associated with the display comprising the steps of : determining the maximum angle A from perpendicular from the said display surface for which touch selection is allowed free from parallax-induced errors; and providing a guard band (36-39) around each touch-selective area (32-35) of the display where the width P of the guard band is the product of T times tan A2 where A2 is the reciprocal of R divided by sin A.

Claim 7

The process in accordance with Claim 4 wherein said guard band is invisible and the spacing between the edges of any neighboring touch-selective display areas is 2P.

Claim 8

The process of avoiding parallax-induced errors in an electronically-generated display visible at the inner surface of a cathode ray tube (10) having a face plate of a thickness Tg of transparent media having a refraction index Rg with a touch-sensitive panel overlaying said display face where the panel has a thickness Tp and a refraction index Rg, and where the display is to function as an input device to a data processing system (18), or the like, by detecting the touching of said panel in areas associated with the display at the cathode ray tube inner surface comprising the steps of: determining the maximum angle A1 for the viewer's line of sight from a line perpendicular to the plane of the display inner surface for which touch selection is allowed free from parallax-induced errors; and providing a guard band (36-39) around each area (32-35) of the cathode ray tube display which is touch selectable at the touch panel where the width P of said guard band is defined by P = (Tg + Tp) tan A2 wherein A2 = 1/(Sin A1)/Rg.

Claim 9

The process of avoiding parallax-induced errors in an electronically-generated display visible at the inner surface of a cathode ray tube (10) having a face plate of a thickness Tg of transparent media having a refraction index Rg with a touch-sensitive panel overlaying said display face where the panel has a thickness Tp and a refraction index Rg, and where the display is to function as an input device to a data processing system (18), or the like, by detecting the touching of said panel in areas associated with the display at the cathode ray tube inner surface comprising the steps of: determining the maximum angle A1 for the viewer's line of sight from a line perpendicular to the plane of the display inner surface for which touch selection is allowed free from parallax-induced errors; and providing a guard band (36-39) around each area (32-35) of the cathode ray tube display which is touch selectable at the touch panel where the width P of said guard band is defined by P = (Tg + Tp) tan A2 wherein A2 = 1/(Sin A1)/Rg.

Claim 10

The process in accordance with Claim 6 wherein said providing step establishes an invisible said guard band with at least 2P separation between visible boundaries of touch-selectable areas on the tube display.